1. Field of the Invention
The present invention relates to a portable device for caching radio frequency identification (RFID) tag data, and a method thereof. More particularly, the present invention relates to a portable device and a method thereof, which stores read tag data so that if a read command is re-entered within a predetermined time and the stored tag data is still valid, the portable device uses the stored tag data.
2. Description of the Prior Art
With the advancement of wireless technology, a variety of RFIDs are currently available from a simple prepaid bus card and entrance ticket to parking lot to rather complicated access card to the places of high security such as laboratory. An RFID system has been developed to satisfy the people's growing demands for more efficient production method, more consumer satisfactory products, more advanced technologies and effective replacements for barcodes and magnetic cards. An RFID system basically includes an RFID tag and an RFID reader. The RFID tag is a contactless card. The user does not need to insert the tag in the reader. Since the physical contact is omitted, problems such as friction or damage are avoided, and the tag is subjected to less influence by the surrounding factors.
An RFID system can be divided into an active type and a passive type depending on how an integrated circuit (IC) implemented in the tag is driven. The active type system supplies power to the internal battery of the tag, while the passive type system induces electric current using electromagnetic waves received from the RFID reader. Additionally, RFID system can be divided into high frequency system and low frequency system according to the frequency band it uses. The low frequency system uses the frequency of approximately several tens of MHz. Accordingly, the system has relatively short reading distance ranging from 10 cm to 15 cm. The high frequency system uses frequency signal approximately of 900 MHz, and thus has longer reading distance of 1 m to 4 m.
The RFID reader function has recently been incorporated into the portable devices such as mobile phones, personal data assistants (PDAs), and laptop computers to maximize utilization thereof. Accordingly, it is now possible to check data of RFID tags in certain distances using mobile phones. Taking a department store for instance, RFID tags can be attached to the products with storing information about the products, such as price, manufacturer, etc., and the customers can check the information of the products from the RFID tags using their mobile phones. In order to use RFID system in the above way, reading distance of at least several meters needs be secured, and a high frequency system is quite efficient in this regard.
Meanwhile, the existing portable devices with RFID reading function re-reads RFID tag when a read command is re-entered during the execution of the application program. Accordingly, an RFID reader chip of the portable device is driven to transmit electromagnetic waves. The RFID tags within a predetermined distance from the portable device generate induction current when receiving the electromagnetic waves. The IC of the RFID tag is driven by the generated induction current, to transmit predetermined tag information. Portable devices usually change locations gradually. Accordingly, it is quite possible that the same RFID tag is read when a read command is entered within a predetermined time. This means that reading process can be unnecessary, especially when a read command is re-entered within the predetermined time. But the tag reading process is always performed regardless of whether the tag information of the RFID tag has previously been read, to extend the time for checking the tag information.
In the case of a high frequency RFID system in particular, the power consumption is high in transmitting and receiving the electromagnetic waves. This can be a very serious problem in a portable device which has a limited battery capacity.